1. Field of the Invention
The present invention relates to an auto-focusing method and a digital image processing apparatus using the same, and more particularly to an auto-focusing method that drives a focus lens to a final focus position through performing an auto-focusing function within a predetermined lens-driving range in response to a photographing signal, and a digital image processing apparatus using the same.
2. Description of the Related Art
An auto-focusing method for a digital camera was disclosed in U.S. Patent Publication No. 20040130650, entitled “METHOD OF AUTOMATICALLY FOCUSING USING A QUADRATIC FUNCTION IN CAMERA,” by the same applicant of the present invention. According to the auto-focusing method disclosed, the focus lens is controlled to be a target focus position through performing an auto-focusing function within a predetermined lens-driving range in response to a photographing signal inputted from a user in the auto-focusing mode.
Hereinafter, the conventional auto-focusing method will be briefly described.
At first, focus values are calculated at each position of the focus lens while the focus lens is driven in the unit of a step within a lens-driving range. The focus value of each focus lens position is calculated by adding different values between adjacent pixel data.
Then, the maximum focus value within the lens-driving range is selected from the calculated focus values, and the focus lens is driven to the position of maximum focus value. In order to quickly find the maximum focus value within the predetermined lens-driving range, a variation ratio between adjacent focus values is used.
If an illuminance in a photographing area is extremely low, the variation ratio between adjacent focus values is low too because it varies according to the illuminance of the photographing characteristics. That is, if the illuminance of photographing area is low, the accuracy is degraded and the speed of auto-focusing is reduced. Therefore, the auto-focusing cannot be accurately performed in a photographing area with low illuminance according to the conventional auto-focusing method for digital image processing apparatus.